#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	double s = 0, t = 1;
	for (int n = 1; n <= 20; n++)
	{
		t = t * n;
		s = s + t;
	}
	printf("1!+2!+...+20!=%lf\n", s);
	return 0;
}